The present invention relates to the field of powering ports, and more particularly to a controller having a plurality of on-board electronically controlled switches and a dynamic algorithm for powering a plurality of ports.
The growth of local and wide area networks based on Ethernet technology has been an important driver for cabling offices and homes with structured cabling systems having multiple twisted wire pairs. The ubiquitous local area network, and the equipment which operates thereon, has led to a situation where there is often a need to attach a network operated device for which power is to be advantageously supplied by the network over the network wiring. Supplying power over the network wiring has many advantages including, but not limited to; reduced cost of installation; centralized power and power back-up; and centralized security and management.
Several patents addressed to this issue exist including: U.S. Pat. Ser. No. 6,473,608 issued to Lehr et al., whose contents are incorporated herein by reference and U.S. Pat. Ser. No. 6,643,566 issued to Lehr et al., whose contents are incorporated herein by reference. Furthermore a standard addressed to the issue of powering remote devices over an Ethernet based network has been published as IEEE 802.3af -2003, whose contents are incorporated herein by reference.
An Ethernet switch or midspan module providing power over Ethernet functionality is typically designed to support a plurality of ports, and power is preferably to be supplied to compatible equipment rapidly after detection. Power is typically supplied under control of a power over Ethernet controller, the power over Ethernet controller energizing for each port to be powered an electronically controlled switch, which in an exemplary embodiment comprises a power MOSFET. In another embodiment the electronically controlled switch comprises a FET or bipolar transistor. At port start up, the inrush current to a remotely powered device, which typically comprises a large input capacitor, must be limited. In order to reduce cost and minimize the footprint, preferably the required electronically controlled switches are provided embedded within the power over Ethernet controller. Unfortunately, embedding a plurality of electronically controlled switches having associated therewith inrush current limiting functionality leads to thermal issues that must be dealt with.
What is needed, and not supplied by the prior art, is a controller having a dynamic start up algorithm, which enables rapid turn on of a plurality of electronically controlled switches, while taking into account thermal requirements.